It is known to provide a clamping device for connecting a tool head to a tool holder on a machine tool so that the tool is interchangeably mounted in the holder by providing the holder with a bore or socket which can be cylindrical or slightly tapered and frustoconical, and into which a projecting portion or pin of the tool holder engages. The tool holder and the tool head are further connected by an actuatable clamping element which, during the clamping action moves from an inner position to an outer position into recesses in the tool head to so lock the tool head in the holder. Such a clamping arrangement provides a force-fitting and form-fitting connection between the tool head and the tool holder.
In German Pat. No. 30 07 440, for example, a tool clamping device is described in which the tool holder is provided with a clamping element movable with a predetermined stroke and which engages radially outwardly effective clamping pins. The latter engage in recesses in the tool carrier to arrest the latter in the holder.
In German Pat. No. 36 02 247, there is described a further clamping device of this type in which a clamping slide is movable in the longitudinal direction of the tool holder and has at its end face a formation which cooperates with the planar surface of a blind bore in the tool head and wherein, in the forward part of the latter, radially movable clamping jaws are provided which cooperate with a pin fixed in the tool holder so that, upon shifting of the jaws against the pin, the latter engages in a groove in the receiving bore of the tool head and locks the tool head in a position in which a shoulder thereof lies against a countersurface or shoulder of the tool holder.
U.S. Pat. No. 4,747,735 discloses a clamping device with a clamping pin by means of an axial shifting of which, clamping bores can be moved radially outwardly. This system operates in principle in manner as the system described in German Pat. No. 30 07 440 to allow the balls to engage in recesses in the tool carrier and to arrest the latter in the housing.
Other patent documents utilize helical or screwthread arrangements to effect a clamping action. These documents include patent cooperation treaty application PCT/US87/02976 filed Nov. 13, 1987 and published July 28, 1988 as WO88/05358. In German Pat. No. 34 10 154, another system basically similar to the pin in drive arrangement utilizing a linearly displaceable camming surface is described. In this case as well, a screwthread arrangement is provided.
In German Patent Document 20 63 186 a powered clamping device engaging a finger behind which the clamp grips, is described.
Independently of the clamping elements used in these state of the art systems, a linear movement is converted into an inclined displacement or a screw or helical arrangement is employed. With a comparatively short clamping stroke, it is possible with these systems to generate high clamping forces, although comparatively complex, expensive or engaging means may be required to maintain the high clamping force. With respect to screwthread arrangements, the angular displacement must be considerable for a limited axial displacement or effect and this may not always be desirable.
Furthermore, especially in the case of screwthread arrangements inordinate amounts of play may be provided.
By and large, therefore, existing clamping devices for the tool head or carrier in a tool holder of a machine tool has not always been satisfactory heretofore.